Airbags that restrain an occupant in the event of a vehicle collision or the like include an airbag that has a left airbag portion and a right airbag portion that inflate in front of the occupant on the left side and the right side, respectively. These left and right airbag portions are inflated by a common inflator. A folding method of this airbag is described in JP, A, 2007-45190.
In the prior art, when the airbag is to be folded, first the left airbag portion and the right airbag portion are each placed sideways. The left airbag portion and the right airbag portion are then respectively flattened in a top-bottom direction and front-back direction. Next, the left airbag portion is folded from the upper end and lower end toward the center along the top-bottom direction into a roll or accordion shape along the top-bottom direction, thereby forming a long, narrow strip-shape in the front-back direction. Similarly, the right airbag portion is folded from the upper end and lower end toward the center into a roll or accordion shape along the top-bottom direction, thereby forming a long, narrow strip-shape in the front-back direction. Subsequently, each of these folded bodies of the left and right airbag portions is folded in a manner that decreases the length in the front-back direction, thereby forming a final folded body of a block shape.
In the prior art, once the left and right airbag portions are folded into long, narrow strip-shapes in the front-back direction, each portion is folded in a manner that decreases its length in the front-back direction. In consequence, when the airbag is inflated, the left and right airbag portions first unfold and deploy in the front-back direction, and subsequently unfold and deploy in the vertical direction, and subsequently deploy in a manner that increases its width in the horizontal direction. As a result, once the airbag begins inflating, a relatively long period of time is required for the left and right airbag portions to deploy across a wide range in the vertical and horizontal directions.